ND Filters And Exposure Tools
ND filters. So ND filters for us filmmakers are just, they're just not an option. I mean, they're not, they are, we have to use them is what I'm trying to say, to get our exposure right. If we want proper motion blur. I mean typically you get your, your phantom in the mail. You go out and fly it. And you haven't got your ND filters. You go back and everything just looks real staccato. So, there's a lot of different makes. Some of you may be familiar with Polar Pro. And, I think they started out on Shark Tank. That show, I think they, they first got their funding through them. And they were just making ND filters. And they started making drone specific ones. So, I have, I usually keep a collection from, you know, all the way from like one stop all the way up to six stops of ND. I mean that's just basically blocking down the light going to the camera. So that way you're able to run a 2.8 aperture and still get a decent exposure. One thing that I use out in the field a lot with, you know,...
especially with the phantom I use a light meter quite a lot. It might seem like overkill in some sense. But, because you do have exposure metering in the app. But what this does is you can actually put in what ND strength you're gonna use. And it'll tell you whether or not you're, like you can take a reading, put in what ND you're gonna use, and it'll tell you whether or not, you know, a 2.8 is gonna work for you. And I usually get it close and then I can ride it up or down with the ISO. 100 to 400 and you're usually in the, you're usually good to go. So this is the Sekonic, s e k o n i c. It's a pretty popular light meter. The 478. I use that a lot. There was, there was, this other drone that I had it didn't have as many exposure metering tools. Like it didn't have, are you familiar with what zebras are? Besides the animal. Zebras are like, it's like a zebra line pattern. That you can turn on on a lot of camera monitors, professional camera monitors. But DGIs actually offered this. They call it overexposure warning. I guess zebras had a patent on their name. So. No but, the exposure warning, and it'll show zebras when you get above 100. Where you're, it's showing you're clipping your whites. Your highlights. So, but on this other one, I didn't have all that stuff so I would just take a meter on the ground. And then that would help me get my exposure just perfect. That's what I was using on those Iceland shoots there. So, another, you can use a variable ND as well. The trick with ND filters on drones is that you wanna make sure you, that you don't get one that's too heavy. Or I suppose maybe too light. But that's never the case. But, these gimbals need to be fairly well balanced. So as you can see right now it's, this one's not really well balanced. They'll handle it within range. But like right now, I've actually got a little weight ring. I'll show you here. I mean not only do I have a step-up ring. There's actually an additional ring on top of my step-up ring that's just there to put weight on the end of the lens. It's just to balance it more. 'Cause if you, if it's not balanced it, you'll start getting these micro-vibrations in the gimbal. That's not usually an issue with the smaller birds that have just a dedicated lens. But if you have, if you're putting on different types of lenses like in the case of this X5, some lenses are heavier than others. And they won't balance properly. And then you'll get these vibrations in your shots. So, that's the one thing about that. So ND filters, they're key, they're a key tool for getting, not only your exposure spot on, but also more importantly really their role is to make sure that you get the right amount of motion blur in your image. So when you first get your drone, it's not gonna come with ND filters. At least mine didn't. And, you'll go out and shoot, and say you're shooting, say you decide you wanna shoot at 60p. So you want your shutter speed to be twice that. So you would set your shutter speed to 1/120th of a second. And you go out on a nice amazingly sunny day, the forecast did not call for this. But the suns out. I'm probably getting sunburned as we speak. But, you'll find that at 1/120th of a second, it's, the shot's gonna be over-exposed. This, these, the little guy, the phantom four has a fixed 2.8 aperture. So at F2.8, ISO 100, 1/120th of a second, you're gonna be over-exposed. And so, the way around that, typically what we would do when we're just starting out with video or whatever is we would just crank your shutter speed until it's fast enough that it compensates and you get your exposure right. You come back and you start editing. And you look at it. And it just doesn't feel right. And what that is is that, the faster you start going with that shutter speed the more staccato the images are gonna look. They're gonna look very sharp and very staccato. And, while sharpness may seem like a good thing in the beginning, it starts looking pretty unnatural the more that you start looking at images that have a faster shutter. And to give you an example of that what you can do is, if you just wave your hand in front of your face like this, you'll see that even at a, even moving slow, there's motion blur. I don't quite understand how that works with our own vision. But it's just true. There's motion blur. So to get proper motion blur in your images you need to make sure that your shutter is at an appropriate speed. The rule of thumb, and it comes from this 180 degree rule from film cameras, but the rule that we follow with shooting digital video is we like to have our shutter speed to be twice as fast as our frame rate. So this morning here, we were filming at 60p. Or 60 frames a second. So I had my shutter at 1/120th. And like I said before, the shot in the early morning was fine without an ND. But as it starts to get bright, it's gonna be over-exposed. So what we do is we put on an ND filter. This one is called a fader filter, or a variable ND. So as I twist this, this is actually two ND filters stacked on top of each other. And as you reorient them relative to each other it stops down the light more or less. Variable NDs are handy in one sense because they, you don't have to take, keep taking ND filters off. You can just have this one on there and as it gets brighter you can just twist it a little bit. Stop it down. Stop the light down even more. The one down side of this is that unless your ND filter has really nice markings on it, which this one just has like varying dots. Which does me really no good. You kind of have to eyeball it. So most of the time what I use are just, I don't know what you call them, just basic ND filters, non-fader, static ND filters. We'll call 'em static NDs. So for example, right here, a lot of different companies make 'em. Polar Pro. They make a ton for, specifically used for drones. Drone cameras often times have specific ways that the filter will have to attach. Either they'll slide on or they have these proprietary clips. Or in the case of the phantom four there is, there are threads but, anyways, Polar Pro does a good job of making filters specifically for certain drone models and brands. So right here, we've got a set of their darker NDs or their stronger NDs. It goes from an ND 16 to an ND 64. And I don't know why some NDs are on a scale where it goes .3, .6, .9, 1.2, 1.5, and each step is an additional stop of light that you can stop down. Polar Pro uses the standard where it's like ND two, four, let's see, two, four, eight, 16, 32, 64. And those are the various stops of light. I'm sure somebody out there that is a super camera nerd could tell me why those different standards were developed. I would just love to see them say one, two ,three four, five, six. 'Cause that's what I'm looking for is like, when I see that I'm a stop under, I wanna know that I need, well sorry if I'm a stop over, I wanna know that my ND I'm gonna grab out of my bag it will give me a stop down so that my exposure is spot on. So, with that, one tool that I've been using to help get exposure right when we're on the ground is using a light meter. And this may seem like overkill for maybe a lot of folks. But when you're dealing with drones that have a fixed aperture like the phantom, phantom has a fixed 2.8 aperture, it's nice to use a light meter. 'Cause what you can do, I'll turn it on here, what you can do on the light meter is you can actually set it, there's different modes right? This is the Sekonic light master pro 478. It's very, a lot of people use these. So in this light meter here, what I have it set to, the mode that I have it set to is shutter mode. So, this actually has, the little guy, the phantom four has two things that we should keep fixed. One is, that we can't change at all, is the aperture. The aperture's 2.8. The shutter though we also wanna keep, ideally we wanna keep it fixed. If we're shooting at 60 like I said, we're gonna shoot at 1/120th of a second. This one actually says 1/125th, so we're close enough. And so what we wanna do is, there's also a section in here, and I could show you guys in the studio, where you can actually put your filter compensation. So you can say, you know, what happens if I put a two stop filter in there? It will tell you based on your aperture, sorry based on your shutter and based on your ISO and based on the filter that you choose, what the aperture needs to be to have a spot on exposure. So, you know, you kind of trial and errored a little bit. But you get close to that aperture, and then you know if you're close to say, it's at 1/120th, ISO 100, and if it says close to 2.8. Maybe it says 3., right now it says 3.6. But if you're close enough, then the one thing you can change in the phantom four of course is the ISO so you could bump up or down the ISO. In the case of, like the larger birds, like the Inspire, where you've got a variable aperture, you of course can change your aperture around a little bit. So, obviously if you change the aperture around it's gonna have some effect on depth of field. But when you're filming aerials, you want a long depth of field. So it's, you're typically working within a range that you're still gonna get your infinity, hyperfocal, everything in focus kind of focus point, which we'll talk about in another installment. But this light meter can be really handy for working with ND filters. You get it right on the ground. Basically the way that it works, is say for example we're out here, we're tracking a surfer from, we'll have the drone, like, here we go. Surfer's here. Drone's here. And we're moving along together. Well, so what I'm doing is I'm trying to get a good exposure on that surfer's front. And so what you want to do with the ND, I mean with the light meter is you wanna meter like you were metering somebody right here. You would meter just like right here. So you take a reading. And it will then tell you whether or not your ND filter choice was spot on or not.